Field of the Invention
The present invention relates to an inhaler.
Description of the Related Art
The invention has been specifically designed for a simulated cigarette device having a generally cigarette-shaped body. However, the invention relates to a development of the outlet valve for such a device which has broader applications in the field of inhalers, for example, medicinal inhalers for oral drug delivery such as asthma inhalers.
In the field of cigarette replacements, there have been a number of proposals to create a simulated cigarette. Such a device has a number of advantages over traditional nicotine replacement therapies such as patches and gum in that they recreate the physical act of smoking which is psychologically important to a smoker, and also are able to deliver nicotine as a dose which more closely replicates the pharmacokinetic effects of a cigarette that persistent smokers desire. Thus, a smoker is able to obtain the “hit” that is familiar from a cigarette, rather than having to deal with the slow release from a patch or gum which does not produce such a hit which leads to unpredictable dosings and poor craving scores and cessation rates.
A simulated cigarette has a reservoir of inhalable composition and an outlet valve which can be triggered, for example, by pushing a button or biting on the end of a cigarette. However, a preferred mechanism for opening the valve is to provide a breath-activated valve as this ensures that the cigarette will only dispense when the user sucks on the device in a manner of a normal cigarette.
WO 02/45783 discloses a drug dispenser having a valve arrangement suitable for dispensing a metered dose. This takes the form of a flexible tube which is wrapped around a valve element and has a pair of kinks. The portion of the tube between the kinks is able to retain a metered dose of the drug to be dispensed. When a user sucks on the dispenser, the valve element moves opening the downstream kink in order to dispense the metered dose. On exhalation, the valve moves in the opposite direction closing the downstream kink and opening the upstream kink to allow the portion of the tube between the kinks to be re-charged with the drug. This arrangement only ever allows a user to inhale one metered dose no matter how long they suck on the device.
U.S. Pat. No. 4,393,884 discloses one such device which has a large resilient “tongue” with a flow path passing through it. This tongue is biased into a first position in which it is out of alignment with the outlet of the cigarette and can be sucked into a second position in which it aligns with the outlet of the cigarette to provide a flow path from the reservoir to the outlet. Such a device is difficult to seal in the first position. It will also require considerable force in order to suck the tongue to the open position against the action of a retaining spring and the relatively large mass of the tongue means that it will be difficult to return to the closed position meaning that dispensing will continue after the suction has been removed.
U.S. Pat. No. 6,889,687 discloses a further example of a simulated cigarette with a breath-activated valve. This discloses a number of examples. One of these has a pair of magnets, one of which is retained by a flexible membrane which allows the magnet to moved apart when suction is applied to a device. This opens up a flow path from the reservoir. However, the mechanism is reasonably complex, has a tortuous flow path which is likely to impede delivery of the composition from the reservoir, and is “binary” in nature in the sense that the valve is either open or closed. It does not provide the ability for the user to regulate the amount of flow by varying the degree of suction. A second example is a spring-biased plunger which is moved axially to open up a passageway in a central rod. Such an axially movable plunger is undesirable in practice as it has been found that the level of suction required to overcome the spring biasing force is too high to be usable in practice. Also, the flow path in the open position is out of the rod, into the plunger and back into the rod so that it is again somewhat tortuous. The third example relies on a magnetic interface where the force on which is overcome by a system of vanes which rotate about the axis of the device, thereby moving along a cam surface to pull the magnetic valve element from its seat. Again, this suffers from problems of complexity, lack of control and a tortuous flow path.
WO 2009/001082 which is our own earlier application discloses two different breath-activated devices. The first of these has a pair of vane systems rotatable about an axis perpendicular to the main axis of the device to align an orifice with the outlet orifice from the reservoir enabling dispensing. The second of these has a pair of hinged flaps which are sucked down against the action of return springs in order to open the flow path. While this solves some of the problems in that it provides a simple mechanism and an axial flow path, the force required as suction to trigger the device is comparatively large and the user, as a result, can exert less control over the system to release a variable dose, small or large according to the inhalation intake.
The present invention is aimed at providing an improved breath-operated valve for an inhaler and, particularly, a simulated cigarette.